// 接口中的常量
trait Circular {
    const PI: f64 = 3.14;
    fn area(&self) -> f64;
}

struct Circle {
    rad: f64,
}

impl Circular for Circle {
    fn area(&self) -> f64 {
        Circle::PI * self.rad * self.rad
    }
}

// 枚举和结构体中的常量
enum Item {
    One,
    Two
}

struct Food {
    Cake: String,
    Chocolate: String
}

impl Item {
    const DEFAULT_COUNT: u32 = 34;
}

impl Food {
    const FAVORITE_FOOD: &'static str = "Cake";
}

fn main() {
    let c_one = Circle { rad: 4.2 };
    let c_two = Circle { rad: 75.2 };
    println!("Area of circle one: {}", c_one.area());
    println!("Area of circle two: {}", c_two.area());
}
